You're going to need heat shielding between the two (exhaust and turbo outlet). Those o-rings will be nitrile, buna or something similar. You can google up their temperature limits, but I think you can take it for granted that with a black surface absorbing radiation of a f**king hot manifold, they will get damn hot. I would wrap the clamp in fibre insulation (think thin kaowool blanket) and then some reflective tape, and try to get a sheetmetal radiation shield layer in between that and the manifold with an air gap either side.